Get start date of marriage through a Wikidata SPARQL query

Question

I would like to change this query which only provides the start date of marriage for one item (wd:Q42)

WHERE {wd:Q42 p:P26 ?statement.   
       ?statement ps:P26 ?spouse;
                  pq:P580 ?starttime;
                  pq:P582 ?endtime.   
      SERVICE wikibase:label { bd:serviceParam wikibase:language "en". } 
} 
ORDER BY (?starttime)

to work for multiple items (e.g. all writers, all citizens of US).

Answer 1

Use a variable (?foo) instead of wd:Q42.

Then you have three options:

• Leave it like that to query all items.
  (Not a good idea if the additional triple patterns aren’t restrictive enough.)
• Add triple patterns using the ?variable to narrow down which items to query.
  (Just like you did with ?statement.)
• Provide a list of subjects that should be queried (using VALUES).

Example for querying writers (occuption = Q36180):

SELECT ?writerLabel ?spouseLabel ?starttimeLabel ?endtimeLabel
WHERE {

  VALUES ?writer { wd:Q42 wd:Q47087 }
  
  ?writer p:P26 ?statement_spouse ;
          p:P106 ?statement_occupation .
  
  ?statement_occupation ps:P106 wd:Q36180 .
  
  ?statement_spouse ps:P26 ?spouse ;
                    pq:P580 ?starttime ;
                    pq:P582 ?endtime .   

  SERVICE wikibase:label { bd:serviceParam wikibase:language "en" . } 

} 
ORDER BY ?starttime
LIMIT 10

By commenting out the VALUES line, you would query all writers instead of just the two listed.

---

Note that your query requires an end time. To also find ongoing marriages, you can use OPTIONAL for that triple pattern:

  ?statement_spouse ps:P26 ?spouse ;
                    pq:P580 ?starttime .

  OPTIONAL {
    ?statement_spouse pq:P582 ?endtime .
  }